Effects of Exogenous Progesterone on Corpora Lutea Induced in Anestrous Ewes

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Abstract
The effects of exogenous progesterone on corpora lutea induced in anestrous ewes were studied in four experimental groups: (1) no progesterone, (2) 25 mg. progesterone per day for 6 days prior to ovulation, (3) 25 mg. progesterone per day for 6 days beginning on the expected day of ovulation and (4) 25 mg. progesterone per day for 12 days beginning 6 days prior to ovulation. The ewes were killed 6 days after the expected day of ovulation. The average corpus luteum weight and the number of ewes for these groups were, respectively: (1) 260.6 mg., 14 ewes; (2) 117.5 mg., 14 ewes; (3) 329.5 mg., 15 ewes; (4) 90.4 mg., 15 ewes. Progesterone injections beginning the expected day of ovulation did not reduce corpus luteum weight. Progesterone injections prior to the time of ovulation resulted in smaller (P<.01) corpora lutea whether or not the injections were continued after the time of ovulation.